Power conversion for the majority of electronic equipment utilizes power supplies that convert power from one form to another. Typically the AC line power of 120 volts is full wave rectified to DC and then this DC voltage (which may be variable or unstable) is controlled by an analog type power supply to, for example, provide a DC voltage of 12 volts. Where the power supply must provide invariable DC voltage or a closely regulated output voltage, analog feedback is used which compares the output voltage of the power supply to a reference. And typically the error voltage may drive a switch with a pulse width modulated (PWM) signal. A very common type of analog power supply of this type is a switchmode supply where an inductor is switched between input and output sides of the power supply to provide well known modes of operation such as buck, boost, inverting, flyback, etc.
Such power supplies suffer several drawbacks such as the variation of parameters in analog components, a difficulty in adjusting to different operating conditions, changing operating conditions, and in general, a relative operational inflexibility especially when applied to a host electronic system which has complex demands.